I like keeping an eye on OpenRouters view of the market: https://openrouter.ai/rankings#market-share

Since the start of the year the market has shifted from 50/50 split (closed v open weights) to 30/70 (70% of usage they see through their platform - is now open weight)

DeepSeek V4.1 Flash 1017 sees 5x the weekly token usage through OpenRouter than the closest closed weight model (GPT-6 Luna)

Even though OpenRouter is only one limited view of the market - those trends should be worrying to potential investors.